X-rays Reveal Distorted Electrons in Iridium Compound

As an electron orbits an atomic nucleus its energy is altered due to the interaction between its spin and an effective magnetic field from the nucleus. This interaction, known as the spin-orbit interaction, becomes important for heavier elements, such as iridium. Recently, a number of new materials containing iridium have been synthesized. These are predicted to have unusual properties due to the spin-orbit interaction, which modifies the shape of the electron cloud, namely the electron's "wave function."  Now, researchers, led by a team at Brookhaven National Laboratory, have measured this shape for the first time. Working with scientists at Argonne National Laboratory, Dresden and the University of Kentucky, they used a technique called inelastic x-ray scattering to excite the electrons and deduce the wave function of the iridium electrons. Rather than the isotropic, cube-like shape expected, they found that it looked more like a bar bell. Since this shape determines how each electron interacts with its neighbors, this has important consequences on the magnetism in these solids and means that the theoretical work will have to be revisited.

This work was published on October 12, 2012 in Physical Review Letters: X. Liu, Vamshi M. Katukuri, L. Hozoi, Wei-Guo Yin, M. P. M. Dean, M. H. Upton, Jungho Kim, D. Casa, A. Said, T. Gog, T. F. Qi, G. Cao, A. M. Tsvelik, Jeroen van den Brink, and J. P. Hill, "Testing the Validity of the Strong Spin-Orbit-Coupling Limit for Octahedrally Coordinated Iridate Compounds in a Model System Sr3CuIrO6" Phys. Rev. Lett 109, 157401 (2012).

This work was supported by the U.S. Department of Energy Office of Science.

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